Power transmission



.March4, 194l. #LROBLNSON Y 2,234,009

POWER TRANSMISSION Filed April 3, 1939 2 Sheets-Sheet 1 F m. I I8 36 5eM I6 4 r l2 H l J J FIG. 8

- INVENTOR JAMES ROBINSON ATTORNEY March 4, 1941. J. ROBINSON POWERTRANSMISSION Filed April 5, 1939 2 Sheets-Sheet 2 JOG RETURN v RUNNINGCUT INVENTOR 'JAMES ROBINSON /T/WM ATTORNEY Patented Mar. 4, 1.941 I l IUNITED STATES PATENT OFFICE rowan TRANSMISSION James Robinson, Detroit,Mich, assignor to Vickerslncorporated, Detroit, Mich, a corpo- I Iration of Michigan Application April s, 1939, Serial No. 265,712

6 Claims. (01. 103-38) This invention relates to power transmissions,any machine tool or other mechanism requiring I particularly to those ofthe type comprising two an alternately reciprocating drive.

or more fluid pressure energy translating devices, Formed in the base I8.is an oil sump indicated one of which may functionas a pump and anat28. Mounted on the base 18 is a prime mover, other asafluid motor. suchas an electric motor 28, whichis directly The invention is particularlyconcerned with a coupled to a variable displacement pump 28. hydraulicpower transmission system adapted for The latter may be of anywell-known suitable driving the reciprocating table of machine toolstype and is illustrated as of the type shown in such as planers,shapers, etc., where a wide range Thoma Patent No. 1,931,969. The pump.28 is of cutting speeds is required with high return connected byconduits 88 and 32 with a variable 10 speed, and also where it isnecessary to provide displacement hydraulic motor 88 which may be formanual "jogging of the table and for stopsimilar in construction to thepump 28. The ping the same. motor 84 has its output shaft connected by aIt is an object of the present'inve'ntion to propinion 38 to a rack 88secured to the table l6.

. vide an improved power transmission system Suitable relief valves 48and 82 are provided in 15 adapted forthis use and which incorporates athe conduits and 32 respectively for bypassing variable stroke pumptogether with a novel con- -oil from one conduit to the other throughbypass trol mechanism for regulating the stroke of the connections 44and 48 whenever the pressure in pump in forward and reverse directions.either line exceeds a predetermined maximum as A further object is toprovide a power transdetermined by the setting of the relief valves. 20mission system of the character described wheree Referring now to Figure2 the motor 26 is in a variable displacement motor is utilized foradapted to drive, by means of a belt drive 48, an providing rapid returnspeeds together with conauxiliary pump 58 of any suitable construction.trol means therefor which automatically'main- The latter has a suctionconduit 52 connecting 2 tains the motor in slow speed setting duringwith the sump 24 nd livery conduit 54 which 25 jogging operations andduring the stopped concarries a suitable relief valve 58 for bypassingoil dition. to the tank through a conduit 58 whenever a pre- Furtherobjects and advantages of the present determined pressure is exceeded inthe line 54. invention will be apparent from the following dee linecommunicates y a branch 50 w a scription, reference being had to-theaccompany- P cheek ves 52 and 5 which connect y 30 ing drawings whereina preferred form f the conduits 88 and 88 with the main line conduitspresent invention is clearly shown. 30 d 32. thus providin r sup r haren f In the drawings: the suction side of the main hydraulic circuit fromFigure 1 is a side view of a planer incorporating h auxiliary p p 5 apreferred form of the present invention, a por- The pump 28 is providedwith aswinging yoke tion of the mechanism being cut away to illustrate19 e Purpose O controlling h a e and the interior construction. ir tionof the discharge of the pump. The po- Figure 2 is a diagrammatic view ofthe hysition of the yoke 18 is controlled. by a multiple draullc circuitincorporated in the mechanism of fluid-motor gen y desi ed as The l t40' Figure 1. ter comprises a stationary cylinder member 14 40 Figure 3is a hart of the elements of a hyhaving a central small-diameter piston"acting draulic circuit and a table illustrating the flow in cylindercham rs 8 d 8- h p st n 16 conditions under various settings of thepilot is connected to the yoke I8 by an operating arm valves. 82.Adjacent the cylinder chambers 18 and 88 Referring now to Figure 1,there is illustrated there are provided a pair of enlarged cylinder 45aplaner embodying abase 18 on whichismounted chambers 84 and 88 in whicha pair of largera frame structure l2 forming a housing for the diameterpistons 88 and 98 are mounted. Cylhydraulic mechanism. Suitably mountedon inders 84 and 88 are of such length that their ways ll on the frameI2 is a reciprocable table l8 respective pistons can never move thepiston 16 adapted to carry a work piece suchas 18 for recompletely intoneutral position but stop at a po- .50 ciprocating movement underneath atool 28 carsition somewhat short of neutral providing for ried by ahorizontally and vertically adjustable positioning the yoke I8 in eitherof two shorttool holder 22. The elements of the planer itstrokepositions. self are intended as illustrative only, it being To the rightand left of the cylinder chambers understood that the invention may beapplied to 84 and 88 there are provided a second pair of 55 chambers 92and 94 which may be of the same diameter as the cylinders 84 and 86.Slidably mounted in the chambers 92 and 94 are a pair of pistons 96 and98 having stems I and I02 5 adapted to abut the pistons 88 and 90respectively. These stems are further provided with reduced portions I04and I06 adapted to extend through central apertures in the pistons 88and 90 and to abut the ends of the piston I6 when the pistons 2 10 asand 9a are in the position illustrated. In this position also the stemsI00 and I02 abut the pistons 88 and 90 which in turn are in abuttingengagement with the end shoulders of the cylinder chambers 84 and 86.Adjustable screw stops I08 and H0 are provided in the ends of chambers92 and 94 to variably limit the outward movement of pistons 96 and 98.

The motor 34 is provided with a swinging yoke II2 for the purpose ofvarying the displacement thereof. An adjustable stop screw II3 variablydetermines the maximum displacement position of yoke I I2. The yoke isconnected by a link II4 with a stem II6 of a piston II8 reciprocablycarried in a stationary cylinder I20. The stroke of 5 the piston I I 8is such that the yoke II2 can never be moved beyond a certainfixedminimum displacement position.

For the purpose of controlling the position of the yokes 10 and H2 thereis provided a pilot control circuit consisting of two pairs of fourwayrotary pilot valves, the valves of each pair being mounted on a commonoperating stem. One such pair comprises valves I22 and I24 which have anoperating handle I26 for manual positioning thereof and are furtherprovided with a pair of trip levers I28 and I30. The lever I28 ispositioned in a plane parallel to the plane of the paper which is behindthe plane of the trip lever I30. These trip levers are positioned in thepaths of adjustable trip dogs I32 and I34 mounted on the table I 6whereby the pilot valves I22 and I24 may be shifted at opposite ends oftravel of the table I6 in the well-known manner. The other pair of pilotvalves comprises valves 5 I 36 and I 38 which are provided with a commonoperating handle I40 movable between the three positions-illustrated inFigure 2.

Each of the valves is provided with four ports P, T, I and 2 positionedin multiples of twenty-: two and one-half degrees around thecircumference of the body. The plugs of the valves are provided withfour equally spaced lands and with cross bores arranged to transpose theconnections between'ports P and T on the one hand and I and 2 ontheother hand. The plugs of valves I36 and I38 are of the open-centertype, that is, when the spool is in mid position, denoted as jog" inFigure 2, ports I- and 2 are'connected to gether and also connected withport T while port 0 P is isolated from all other ports. Valves of thischaracter being well-known to those skilled in g the art, furtherelaboration of their construction will be dispensed with. p k From theauxiliary pump delivery conduit 54 06 a branch conduit I42 extends tothe port P of valve I38 and the port T of valve I36. A second branchconduit I44 extends. to the portP of valve I22. Tank conduit I46connects by a branch I48 with port P of valve I36 and by a. branch 7 I50with the port T of valve I38. The conduit I46, also connects to port Tof valve I24. Branch conduits I52 and I54 connect to the ports D ofvalves I38 and I22 which serve as seepage drains for each pairof-valves. Port I of valve I36 con? nects by a conduit I56 with port Tof valve I22.

- P and 2 and conduit I58.

Port I of valve I 22 is plugged while port '2 thereof connects by aconduit I58 with the head end of the cylinder I 20. The rod end of thelatter is connected to the auxiliary pump delivery conduit 54 by abranch I60. From conduit I56 a branch 5 conduit I62 extends to thecylinder chambers 84 and 86 of motor I2. Port 2 of valve I38 connects bya conduit I64 with the cylinder chambers 92 and 94 of motor I2. Port Iof valve I38 is plugged. Port 2 of valve I36 cosnects by a con- 10 duitI66 with port P of valve I24. Ports I and 2 of valve I24 connect byconduits I68 and I10 with the cylinder chambers and I8 respecof thetable depends upon two factors, first, the 25 angle of tilt :of the yoke10, the speed increasing with increasing angles of tilt, and second, theangle of tilt of the yoke II2, the speed decreasing with increasingangles of tilt. In other words, the yoke II2 is shown in Figure 2 in theslow speed position. If the yoke I0 be swung counterclockwise away fromneutral position, 011 is delivered to the conduit 32 causing the motor34 to rotate in the direction indicated and operating the table on acutting stroke.

The operation of the pilot circuit for controlling the position of yokes10 and II2 may best be understood from Figure 3 the upper portion ofwhich represents a simplified chart of the pilot circuit and the motorsI2 and II8-I20. In this 40 portion of the chart the pilot valves I22,I24, I36 and I38 are represented as circles, the four ports beingconnectable either cross-wise or parallel as shown in the circles in thelower portion of the chart. I 45 If we consider now the conditions shownin the line marked, Stop" in the lower portion of the chart, it will beseen that pilot pressure from conduit 54 is admitted through conduitI42, ports P- and 2 of valve I38, and conduit I64 to the 60.

chambers 92 and 94. Thepistons 96 and 98 are accordingly moved inwardly,the stems I00 and I02 carrying-the pistons 88 and up against the ends ofchambers 84 and 86. The stems I04 and I06 also abut piston I6maintaining the 55 less of the position of valve I22 since if the latteris in the cross-connection position, pilot pressure flows in fromconduits 54 and I44 through ports If the valve I22 is'in itsparallel-connection position, pilot pressure flows in from conduitI56through ports T and 2 70 i and conduit I58. The chambers 18 and 80are connected to tank at all times regardless of the position of valveI24. Since port T thereof is connected to tank by, conduit I46 and portP thereof is'connected to tank throughbonduit I66, 76.

ports 2 and P of valve I36 and conduit I48. Thus the yoke I ismaintained in neutral position. Referring to the next line of the lowerportion of the chart which illustrates the condition when 6 the handleI46 is shifted to jog position and when the handle I26 is in the cuttingposition, ports T, I and 2 of valves I36 and I36 are all connectedtogether since the Jog position is the open-center condition.Pilotpressure is thus ad- 10 mitted from conduits 54 and I42 throughports T- and 2 of valve I36, conduit I68, ports P and 2 of valve I24,and conduit M0 to chamber 18, thus urging piston 16 to the left. Oil isdischarged from chamber 86 through conduit I68, ports I and .15 T ofvalve I24 and conduit I46 to tank; Pilot pressure is also admitted frompoi-t T of valve I36 to port I thereof and through conduits I56 and I62to the chambers 84 and 86. Pistons 88 and 96 are accordingly maintainedagainst the inner ends oftheir cylinder chambers, and since the piston96. has a greaterarea than the piston", the formeracts as a limit stoppreventing the leftward travel :of piston 16 beyond a minimum strokeposition suitable for jogging speed of the v 25 table I6. Chambers 92and 94 are connected to tank through conduit I64, ports 2 and T of valveI36, and conduits I60 and I46, thus permitting pistons 96 and 98 to moveoutwardly against their stops I68 and H0. It will be noted that in themaximum outward position the stems I64 and I66 do not completely leavethe central bores of the pistons 86 and 96. Otherwise pressure 011 fromchamber 86 would be permitted to bypass into chamber 80 and throughconduit I66, ports I 36 and T of valve I24 and conduit I46 to tank.Pilot pressure is also maintained in cylinder I20to hold yoke II2 inslow speed position, it being admitted from conduit I44, through ports Pand Z of valve I22 to conduit I58.

40 The jogging retum position illustrated on the next line of the lowerportion of the chart is the same as that previously described exceptthat valves I22 and I24 are reversed, causing the piston I6 to shift tominimum stroke position on the return side of neutral as will be clearfrom the chart. Pressure is maintained in cylinder I20 during theseconditions by the connection from conduit I42, through ports T and I ofvalve I36, conduit I56, and ports T and 2 of valve I22 to conduit I58.

The next line of the charts illustrates the conditions when handle I40has been shifted to the rim position, valves I22 and I24 being in thecutting position. The only change over the condition of jogging cutthereby established is that the chambers 84 and 86 are connected to tankthrough conduits I62 and I66, ports I and P of valve I36 and conduitsI48 and I46. This accordingly permits piston I6 to move fully'to the onleft carrying piston 96 with it until the latter abuts stem I62 ofpiston 98.

The last line illustrates the conditions when the valves I22 and I24 areshifted to the return position. Under these conditions the chambers 05I8 and 86 are transposed so that chamber 86 is connected to pilotpressure from conduit I42, through ports T and 2 of valve I36; conduitI66, ports P and I of valve I24, and conduit I68. Chambers 84, 86, 92and 94 remain connected to 70 tank as before. Cylinder I26, however, isalso connected to' tank in this position through conduit I58, ports 2and T of valve I22, conduit I56, ports I and P of valve I36, andconduits I48. Pressure admitted through conduit I to the rod 76 end ofcylinder I20 moves the piston II8 to the left bringin yoke II2 into itsminimum stroke position, thus causing the return stroke to take place athigher speed.

' During normal running operation the dogs I32 and I34 alternatelycontact the levers I28 and 5' I36, shifting the valves I22 and I24between cutting and returning positions at the end of the respectivestrokes of the table I6. There is thus provided a control system which,acting throu h the unitary multiple piston motor I2 and thr h 10 themotor displacement regulator II6--I26, provides for stopping of thetable, for manually op-- erating the same at low speed to producejogging movement, or for automatic continuouslyrepeating cycles ofcutting and high-speed re- 15 turning strokes. The stop screws I08, H0and H4 provide for independent adjustmentsof cutting and return speeds.

While the form of embodiment of the invention as herein disclosedconstitutes a preferred 20 form, it is to. be understood that otherforms might be adopted,- all coming within the scope of the claims whichfollow. I

'What is claimed is as follows:

1. In a hydraulic power transmission system 25 the combination of avariable displacement pump, a member movable to vary the pumpdisplacement, a first piston motor for operating said member through itsfull stroke, a second pis-.- ton motor opposing the first piston motorand 30 operable to limit the stroke of said member to a smaller range, athird piston motor opposing the first piston motor and operable to holdsaid member in neutral, a first pilot valve means movable between aforward and a reverse position as for selectively supplying fluid tothe'first piston motor in either direction to control the direction ofdelivery of fluid by the pump, and a second pilot valve means movablebetween three positions to control the supply of fluid to all three 46piston motors to respectively position saidmemher at neutral, limitedstroke or full'stroke for stopping, jogging or running the fluid motor.

2. In a hydraulic power transmission system the combination of a'variable displacement-45 pump, a member movable to vary the pumpdisplacement, a fir piston motor for operating said member throu itsfull stroke, a second piston motor opposi g the first piston motor andoperable to limit the stroke of said member to a I56 smaller range, athird piston motor opposing the first piston motor and operable to holdsaid member in neutral, said piston motors being mounted in axialalignment and having their pistons in abutting relationship, a firstpilot valve means movable between a forward and a reverse position forselectively supplying fluid to the first piston motor in eitherdirection to control the direction of delivery of fluid by the pump; anda second pilot valve means movable between 60 three positions to controlthe supply of fluid to all three piston motors to respectively positionsaid member at neutral, limlted'stroke or full stroke for stopping,jogging or running the fluid motor. 6

.3. In a hydraulic power transmission system the combination oi avariable displacement pump,- a member movable to vary the pumpdisplacement, a first piston motor for operating said member through itspiston motor opposing the first piston motor and operable to limit thestroke of said member to a smaller range, a third piston motor opposingthe first piston motor and operable to hold said member in neutral, saidpiston motors being 76 full stroke, a second 76 mounted in axialalignment in a continuous cylindrical chamber having portions ofdiffering diameters and having their pistons 01 d-iflerent efiectiveareas and in abutting relationship, and

pump displacement, a first piston motor for operating said memberthrough its full stroke, a second piston motor opposing the first pistonmotor and operable to limit the stroke of 'saidmember to a smallerrange, a third piston motor opposing the first piston motor and operableto hold said member in' neutral, said piston motors being mounted inaxial alignment and having their pistons in abutting relationship, afirst pilot valve means movable between a forward and a reverse positionfor selectively supplying fluid to the first piston motor in eitherdirection to control the direction of delivery of fluid by' the pump,'and a second pilot valve means movable between three positions tocontrol the supply of fluid to all three piston motors to respectivelyposition said member at neutral, limited stroke or full stroke.

5. A fluid motor for selectively positioning a member in any one of fivedifierent positions comprising a pair of oppositely facing cylindricalchambers each having asmall diameter portion.

and a large diameter portion, ram means slidable in said small diameterportions from one extreme position to the other and connected with saidmember, second ram means slidable in said large diameter portionsbetween each extreme position and a less extreme position and arrangedto abut the first ram means, and third ram means also slidable in thelarge diameter portion between each extreme position and an intermediateposition and arranged. to abut the first and secondram means.

6. A fiuid motor for selectively positioning a member in any one of fivedifl'erent positions comprising a pair of oppositely facing cylindricalchambers each having a small diameter portion and a large diameterportion, ram means slidable in said small diameter portions from oneextreme position to the other and connected with said member, second rammeans slidable in said large diameter portions between each extremeposition and a less extreme position and arranged to abut the first rammeans, and third ram means also slidable in the largediameterportionbetween each extreme position and an intermediate position andarranged to abut the first and second ram means, said second ram meanshaving a bore therethrough and said third ram' means having a portionslidably engaged in said bore and extendable through the second rammeans.

JAMES ROBINSON.

